Photoflash system



R. A. STEIN ETAL PHOTOFLASH SYSTEM Sept. 2, 1952 Filed June 21,

INVENTOR. WQQ T M Patented Sept. 2, 1!?52 Ohio, assignors to GlobeIndustries,

ton,"hio, a corporation of Ohio n D w- Application June 21, 1951, SerialNo. 233,427 l2 Claims. (01. 3151- 354) In the normal use in indoorphotography of photoflood lamps, or high amperage incandescent filamentlamps, as a source of illumination, the lamps stay illuminated duringthe preparatory stages. This reduces the useful life of the lamp and inaddition causes considerable annoyance to the subject and to thephotographer.

This application is a continuation-in-part of our copending applicationSerial No. 18,384, filed April 1, 1948, now abandoned, for PhotofiashSystem.

Quiz of the aims of the present invention is to eliminate the fullillumination of the lamps dur: ing the preparatory stages.

In addition, the present invention aims to employ the photofiood highamperage incandescent filament lamp in the same manner as flash bulbs.

In other words, the present invention provides asyst'em of indoorphotography employing high amperage incandescent filament lamps, knownin the trade as photoflood lamps or bulbs at a supernormal illuminationwith the result that snapshots may be taken with great facility. Thesupernormal or high luminosity of the lamp is obtained by imposing uponthe'filament asuper normal voltage and passing through the filament asupernormal current which brings the filament to peak temperatures whichapproxi'mate'the melting point of the filament, vtheduration 'of thispeak voltage, current and temperature, how"- ever, being so short thatthe useful life of the bulb .is 'not materially shortened.

the normal operation of the hood light at rated voltage an interval ofapproximately '100 milliseconds lapses between the "closing of theswitch and the' maximum luminosityproduced by the hood light. In thesystem of the present inventiont'he supernormal luminosity is obtainedwith ,aftime delay of only abOlit' 20' milliseconds or less."Thi's'd'elaycorresponds .to the conventional time delays in solenoidoperated shutter mechanisms of cameras and the present system, thereforecan be readily employed to be operated by such mechanisms and when soemployed will produce the desired peak luminosity at the desired time inthe operation of the shutter."

In the present invention the flood light or tion of the lam maintainsthe filament at a rela: tively hi h empe u and P m ts the time delay inreaching the supernormal luminosity I peak to be not more than 20milliseconds.

Another advantage of the present invention t that as compared with thenormal use of such lamps in which they remained at their ratedluminosity for substantial periods during each exposure lasting intomany minutes, by the use of the present invention, the bulb is employedduring. the same period at reduced luminosity and at a supernormalluminosity for only a short,- time with the consequent increase of theefiective life of the bulb. I

Other objects and advantages reside in the construction of parts, thecombination thereof the mode of operation, as will become more apparentfrom the iollowing description.

A more detailed understanding of the present invention will be had from'the'foll'owing spac ng cation and the accompanying drawings which 1illustrate the preferred embodimentsof the in} vention, it beingunderstood that variationsthereof falling within thescope' of theappended claims will be apparent to persons skilled in the art.

In the drawings, Figure 1 is a diagrammatic" illustration of one'form ofthe invention; Figure 2 is a diagrammatic illustration of the systemshown in Figure 1 associated'wi'th a sale;

noid operated camera shutter."

Figure 3' is a diagrammatic illustration of another iorm of theinvention in which thyr'atrop orphotofiood lamp socket. This impedanceserves to reduce the voltage across the lamp during the modeling orpreparatory stage. lamp or bulb operates at below rated voltage.

When the photograph is about ,to be taken and the shutter is open, asupernormal voltage is then impressed upon the filament so as to producea peak of supernormallum'inosity' Because of the high peak luminosity ascompared with the modeling illumination obtained from the'lamp's', theshutter may be set for any desired time, such as a full se'cond,'ifdesired,'and afterthe shutter is opened, the closing of the operatingswlit'oh'of thefsystem of the present invention will'produce thesupernormal luminosityfor a very'sh'ort' time with the camera shutteropen. Thereafterftlfe" shutter may be closed.' Thus, by'mea'iisol' thepresent invention anexposui'e of approximately- .Therefore, the

3 V25 of a second is obtained with the shutter open for a much longerperiod as desired.

The current flowing through the lamp is sufficiently great to melt thefilament or heater element of the lamp if permitted to flowcontinuously. For a short period of time the surface of the filament isheated to such an extent that extremely high luminosity is obtained.This characteristic is aided when alternating current is used by theskin effect, that is, the current density at the surface of the filamentor conductor is greater than the density in the center thereof. Thethermal capacity of the filament is such that the filament is not heatedthroughout the thickness thereof sufiiciently to melt it within theshort period of time used.

Considering the present invention. more particularly, it provides animpedance coil in series with the photofiood lamps which reduces theoperation of the lamp or lamps to below the rated voltage during themodeling or preparatory stages and the same impedance coil issubsequently employed to have a supernorrnal voltage generated thereinwhich is imposed upon the high amperage The present invention alsoprovidesclosed only for a time, permitting the filaments to reach thedesired supernormal peak luminosity for'thedesired time. Thus, thepresent system may be designed to provide an exposure of about ,6 of asecond or the like. 1

Referring more particularly to the drawings, the'wires H3 and I! may beconnected to any suitable source of A. C. voltage, such as the customaryhousehold 110 volts. The bulbs or bulb sockets l2, two being shown inparallel, are connected on one side to line In through a manual switch13 and a fuse I4, it being understood that any number of such bulbs canbe employed. The winding 15 of the transformer is interposed in line;Thus the winding 15 serves as an impedance or choke coil to reduce thevoltage across the bulbs or bulb sockets to below the rated voltage. Theprimary winding [6 of the transformer isconnected to the Wire 10 at thepoint I! and to the wire I I by means of the wire E8, the latter, I

however, having interposed a variable resistance 50- and a normally openswitch comprising a fixed contact [9 and a movable contact 20.

Thus, when the switch [3 is closed, the fiood lights will operate belownormal voltage and serve to provide the desired light for modeling.Whenswitch I9, 20 is closed, a high voltage will be. induced in windingl5 which is additive to theline voltage and the incandescent filamentswill reach a high supernormal peak luminosity.

The variable resistance 58 controls and may.

be employed. to adjust the high voltage across the photofiood bulbs 12to the desired value. The neon glow lamp 52 bridging part of thepotentiometer resistor 5i serves to indicate when the voltage across thephotofiood lamps I2 equals the desired predetermined value. The resistor50 and glow lamp 52 provide a check and a means for maintaining theapparatus in good operating condition.

The present invention provides for an automatic control of the switchI9, 20 so as to maintain the same closed only for the desired time fromone-tenth to one-hundredth of a second. For this purpose the movablecontact 20 is carried by the armature 2| of the relay 22. One side ofthe relay winding 22 is connected to the line wire H3 through aresistance 23 and rectifier 24 and wire 25. The other side of thewinding 22 is connected to the other line wire ll through the manualswitch 26 and wire 21. A condenser 28 is connected as shown across thewinding 22 and the switch 26.

In operation the line wires i 6 and H are plugged with the source ofline voltage and the switch 13 is closed. The winding I5 of thetransformer serves as an impedance and the bulbs l2 operate at belownormal voltage. At this time the condenser 28 becomes charged to itsmaximum voltage by a charging circuit which includes wire 25, rectifier24, resistance 23, condenser 28 and wire 27. When the exposure is made,the switch 26' is closed and the condenser 28 discharges through theswitch 26 and relay 22. This I moves the armature 2| to close the switchI9,

28 thereby connecting the winding is across the mains. voltage inducedtherein, which is additive to the line voltage so as to produce avoltage of perhaps 175 volts or the like across the photofiood bulbs i2.When the condenser 28 has discharged or its voltage is reducedsubstantially by the discharge, the winding 22 is de-energized and theswitch [5, 25 is opened. By means of this sys- A tern, therefore, theswitch I9, 20 is automatically opened at a predetermined time,preferably ,5 of a second, after it is closed.

Because the filaments had been maintained hot and their circuit is notinterrupted it can be brought to the supernormal peak luminosity withina time delay of less than 20 milliseconds after the high voltage isapplied.

It will now be seen that thepresent system provides for the employmentof a minimum of parts. One winding of the transformer is employed bothto provide the high voltage and the impedance for the bulbs. The size ofthe transformer is considerably reduced by the present system because alarge percentage of the supernormal voltage is obtained directly fromthe line. In the present apparatus the initial or preliminary voltageapplied to the filaments during the modeling stage may be varied byvarying the reluctance in the core of the transformer, as by changing oradjusting the air gap in the core or The time of energizain the corelaminations. tion of the relay winding 22 can be controlled by varyingits resistance, or by varying the size of the condenser, 'or by varyingthe voltage to which the condenser is charged.

When the relay 22 is energized and the cone tacts i9, 28 are closed, thereactance of coil l5 is reduced to a low value and the voltage inducedtherein is built up rapidly. This voltage adds to the line voltageacross the bulbs and causes themto glow at an exceedingly high intensityfor the.

duration of time the relay is closed. By limiting the duration of thehigh intensity illumination to the short period of time and partially asa result of the latent heat of fusion of the'filament, burn out isavoided. The present unit can be synchronized with any camera shutterwhich ;;has contacts that close when the shutter is The winding l5 has arelatively high T me e openedi Such shutter contacts could then be usedas the: switch126, to thereby obtainautomatic synchronization of theflasher the: photofiood lamps.

Where the camera, shutter does not have. contacts; but instead: isoperated by a solenoid, the optional wiring arrangementof the controlcircuiti shown in Figure 2 may be employed. In this figure the boxcorresponds to that part of the system shown in Figure l which isincluded withinthe dottedline box 30. The elementsof' the control shownin Figure l and which also appear inFigure 2 bear the samereferencecharenters.-

the wiring diagram shownrin Figure 2 when theswitch 32, a. double polesingle throw switch, is closed to? operate the shutter and to: create a;flash, thecondenser 28 is'discharged through the relay 22, throughiwire33, switch 32 and Wire 34. The? closing of the switch 32 also energizesthe shutter operatingsolenoid 35' through the circuit which includeswire 31, rectifier 24 solenoid 35 and voltage dropping resistor 36. Thesolenoid thus: acts essentially insynchronization with the relay 22.The. voltage. dropping, resistor 36 reduces the voltage across thesolenoid coil to the-desiredvalue. The by-pass resistor 38 isdesirablein the event that the solenoid coilisnot plugged in, in whichcase it. provides a current pathto charge the condenser. The resistanceof 38-15 very'hlghcolnpared to the resistance; 0f.solenoidcoil 35.

Figure 3 shows. a system which is analogous to: the system. shown inFigure 1. except that i instead of. a relay 22" and contacts- IS, 20operated thereby; one or two' thyratrons' 40' are employed, as shown. Inthis system the thyratrons arenor mally biased to out ch. When theswitch 26 is closed, condenser'zll discharges throughthe primary'winding: 4| of the transformer which is provided with two secondaries 42and 43, one of.

these two secondaries 42, 43, connected in the grid circuit of eachthyratron- 40. The oscillationggeneratedin the circuit which includesthe condenser 28- and the: primary winding-'14! are thereby transferredto the grids of the thyra.-- trons and cause the same to fire, thuseffectuallyconnecting the windin [6 to the line; The thyratronscontinue: firing. until the oscillations dampen out to below the firingpotential of the thyratrons'; The: time of firing is controlled by thecharacteristics. of the transformer; 4 I 42, 43.

The use of a transformer for illuminating a flash bulb: is; not alwaysessential.

or. a second, or thereabouts, when connected across the terminals of anormal line voltage; say 110 volts; could b'eus'ed, as clearlyillustrated in- Figure 4; For example, two- 32 volt flash lamps H2 maybe used to produce afiash when connected across 110 volt circuit. Thevoltage supplied to the'lamps H2 may be reducedfto' 20 volts or someother: subnormal l voltage by' means" For example, a. flash: bulb thatwould flash in a. period of /2 the electromagnetl 22, the switch l9 willagain" be: opened, in that the current flowing. through the leakagecircuitincluding the rectifier 24- and the. resistance 23 isinsufficient to hold the elec tromagneti'lL Although the preferredembodiment'of the de: vice has beendescr-ibed, it will be: understoodthat within the purview of this invention various changes. may bemadeinthe. form, details', proportionand arrangement of par-ts, the combination' thereof andmode of operation, which gen erally'statedconsistin adevice'capableof carrying out the objects set forth, as disclosedanddefined in the appended claims.

Having' 'thus described our invention, we claim:

1. In. an illuminating apparatus for photo-- graphic purposes employinghigh luminosity incandescent filament lamps, the" combination-of areceptacle for said lamp, a-transformer having? two windings, onewinding being connectedin series with said receptacle and serving toreduce the voltage impressed upon said receptacle to substantially belowthe rated voltage of the lamp, the second winding being normally opencircuited, and electric control means operable response to the closingof its circuit to' close the circuit of the second winding" and to openthesame after the lapse of a predetermined srnalli fraction of a second.

2. Ihe apparatus set forth in claim 1 in which the lastnamed meanscomprise a condenser and circuit means receiving a discharge from saidcondenser, said circuit means'includinga sv'vitcli for opening andclosing the second winding, the

' discharge serve to actuate said circuit to close and open the secondwinding circuit.

3; In an illuminating apparatus for photographic purposes employing ahigh luminosity incandescent filament lamp, the combination of anelectrical receptacle for said lamp, a transformer having a primarywinding connected in parallel with said receptacle and normally opencircuite'd and a secondary winding connected in series with saidreceptacle and serving to reduce the voltage at the receptacle, andelectric control means for closing and opening" said primary" winding.

4. The apparatus set forth in claim? in which incandescent filamentlamp, the combination of" a receptacle for said lamp, a transformerhaving two windings, one winding connected in series; with thereceptacle, means for connecting said receptacle and second winding to avoltage source, the second winding connected in parallel with thereceptacle, the circuit of said second winding being normallyopen, andelectric control meansfor closing the circuit of said second windingthe'reby'generating in the one winding" a volta e in a manner to add thesame to't he'" voltage of the source, so as to caus'e'the filament"lamps to flash momentarily then said electric control means opening thecircuitthrough the second winding.

6. In an illuminating apparatus for photographic purposes employing highluminosity" incandescent filament lamps, the combination of a receptaclefor said lamp, a transformer having two windings, one winding beingconnected in series with said receptacle and serving to reduce 7.1 thevoltage impressed upon said receptacle tov substantially? below therated voltage. of the lamp, thesecond winding being normally opencircuited, and control means to close and open the circuit of the secondwinding, said control means closing the circuit of the second winding tocause the filament lampsto flash momentarily then open circuiting thesecond winding.

7 The method of illuminating objects for, photographic purposes by theemploymentof an incandescent. filament lamp having a normal voltagesubstantially equal to normal line volt. age, the steps of impressingupon the lamp a voltage substantially below its rated voltage, charginga condenser, discharging the condenser through a relay, said relayaltering the circuit through the lamp so as to impress upon theterminals or" the lamp a voltage sufficiently high to cause a current toflow through the filament of the lamp, generating sufficient heat tomelt the filament if permitted to continue, the condenser upon beingdischarged permitting the relay to open the circuit through the lampbefore sufficient heat has been generated in the filament to melt thesame.

8. In an illuminating apparatus for photographic purposes employing ahigh luminosity incandescent filament lamp, the normal voltage of thefilament lamp being substantially equal to the normal line voltage, thecombination of a receptacle for said lamp, a transformer having aprimary winding and a secondary winding, the primary winding beingconnected in series with said receptacle and serving to reduce theVoltage impressed upon said receptacle to a voltage substantially belowthe rated voltage of the lamp, the secondary winding being normally opencircuited, and electric control means including a condenser and arectifier connected in series across the terminals of the line and inparallel with the primary winding of the transformer and the filament ofthe lamp, a relay and a switch connected in series across the terminalsof the condenser so that as the switch is closed the condenserdischarges through the relay, said relay actuating a switch forconnecting the secondary windings of the transformer across theterminals of a filament so as to increase the voltage impressed upon theterminals of the filament to cause a current of sumcient magnitude tomelt the filament if permitted to continue to flow, the relay opencircuiting the secondary winding upon the condenser being discharged soas to have a voltage across the terminals less than the voltage requiredto hold the relay switch closed.

9. In a photofiash illuminating apparatus employing an incandescent lampor lamps, means for applying a subnormal voltage to said lamp or lamps,and means for applying a supernormal voltage for a predeterminedinterval of time to said lamp or lamps, said last mentioned meansincluding a relay, a condenser, a switch for connecting the condenseracross the terminals of the relay, and a leakage circuit for chargingthe condenser, the closing of the switch causing the condenser toenergize the relay so as to supply a supernormal voltage to the lamp orlamps, the current through the leakage circuit being insufficient tohold the relay so that the relay interrupts the supernormal voltage uponthe condenser being discharged.

10. In an illuminating apparatus employing an incandescent lamp orlamps, means for applying i a predetermined voltage to said lamp orlamps,

means for varying said voltage, and means for automatically limiting thetime of application thereof to obtain a change in luminosity for saidlamp or lamps for apredetermined interval of time, said last mentionedmeans including a relay for actuating a switch to vary the voltage, acondenser, a leakage circuit for charging the condenser, and a switchfor connecting the condenser across the terminals of the relay, thecurrent through the leakage circuit being insufiicient to actuate therelay, the charge on the condenser upon the last mentionedswitch beingclosed energizing the relay to vary the voltage supplied to the lamp orlamps until the condenser has been discharged at which time only thepredetermined voltage is applied to the lamp or lamps.

11'. In a photofiash illuminating apparatus employing an incandescentlamp or lamps, means for applying a predetermined voltage to said lampor lamps, and means for adding a supernormal voltage to said lamp orlamps to produce a flash, said last mentioned means automaticallylimiting the time of application thereof for apredetermined interval oftime, said last mentioned means including a condenser, a leakage circuitfor charging the condenser, a relay, and a switch for connecting thecondenser across the terminals of the relay, the current required tohold the relay being greater than the current normally fiowing throughthe leakage circuit so that as the switch is closed causing thecondenser to discharge through the relay the relay causes a supernormalvoltage to be applied to the lamp or lamps only until the condenser hasbeen discharged.

12. In a photofiash illuminating apparatus including an incandescentlamp or lamps, an electric circuit connected to the source of energyhaving a voltage input substantially higher than the voltage required toilluminate the lamp or lamps under normal operating conditions, saidcircuit including an impedance connected in series with the lamp orlamps was to reduce the voltage supplied to the lamp or lamps to asubnormal voltage, and circuit means for applying the line voltagedirectly to said lamp or lamps for a predetermined interval of time soas to cause a flash thereof, said last mentioned means including arelay, a condenser, a switch for connecting the condenser across theterminals of the relay, and a leakage circuit for charging thecondenser, the leakage circuit including a rectifier and an impedancefor reducing the current flow so that the current flowing through theleakage circuit is insufiicient to energize the relay but sufilcient tocharge the condenser, the closing of the switch causing the condenser toenergize the relay so as to apply the line voltage to the lamp or lampsuntil the condenser is substantially discharged through the relay atwhich time the relay interrupts the flow of line voltage to the lamp orlamps thereby interrupting the flash thereof.

- ROBERT A. STEIN.

LEE S. WASSERMAN.

No references cited.

